Order.java

package uk.co.initech.sandbox;

import java.util.HashSet;
import java.util.Set;

import javax.persistence.CascadeType;
import javax.persistence.Entity;
import javax.persistence.Id;
import javax.persistence.OneToMany;
import javax.persistence.Table;

@Entity
@Table(name="Order_")
public class Order {
	
	@Id
	private String id;
	
	@OneToMany(mappedBy = "order", cascade = CascadeType.ALL)
	private Set<OrderLine> lines = new HashSet<OrderLine>();
	
	public Order(String id) {
		this.id = id;
	}
	
	protected Order() {}
	
	public String getId() {
		return id;
	}
	
	public void setLines(Set<OrderLine> lines) {
		this.lines = lines;
	}
	
	public Set<OrderLine> getLines() {
		return lines;
	}
	
	@Override
	public int hashCode() {
		return id.hashCode();
	}
	
	@Override
	public boolean equals(Object that) {
		return (this == that) || ((that instanceof Order) && this.id.equals(((Order) that).id));
	}
	
}

OrderLine.java

package uk.co.initech.sandbox;

import javax.persistence.Entity;
import javax.persistence.Id;
import javax.persistence.IdClass;
import javax.persistence.ManyToOne;

@Entity
@IdClass(OrderLine.Key.class)
public class OrderLine {
	
	public static class Key {
		
		private String order;
		private String productId;
		
		public Key(String order, String productId) {
			this.order = order;
			this.productId = productId;
		}
		
		@Override
		public int hashCode() {
			return order.hashCode() + (productId.hashCode() << 1);
		}
		
		@Override
		public boolean equals(Object that) {
			return (this == that) || ((that instanceof Key) && this.order.equals(((Key) that).order) && this.productId.equals(((Key) that).productId));
		}
		
	}
	
	@Id
	@ManyToOne
	private Order order;
	
	@Id
	private String productId;
	
	private int quantity;
	
	public OrderLine(Order order, String productId, int quantity) {
		this.order = order;
		this.productId = productId;
		this.quantity = quantity;
	}
	
	protected OrderLine() {}
	
	public Key getId() {
		return new Key(order.getId(), productId);
	}
	
	public Order getOrder() {
		return order;
	}
	
	public String getProductId() {
		return productId;
	}
	
	public int getQuantity() {
		return quantity;
	}
	
	public void setQuantity(int quantity) {
		this.quantity = quantity;
	}
	
	@Override
	public int hashCode() {
		return getId().hashCode();
	}
	
	@Override
	public boolean equals(Object that) {
		return (this == that) || ((that instanceof OrderLine) && this.getId().equals(((OrderLine) that).getId()));
	}
	
}